Disallow users modify canvas after it transfers control to offscreen

third_party/WebKit/Source/core/html/HTMLCanvasElement.h

 /*
  * Copyright (C) 2004, 2006, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 70 matching lines @@
 
     DECLARE_NODE_FACTORY(HTMLCanvasElement);
     ~HTMLCanvasElement() override;
 
     // Attributes and functions exposed to script
     int width() const { return size().width(); }
     int height() const { return size().height(); }
 
     const IntSize& size() const { return m_size; }
 
-    void setWidth(int);
-    void setHeight(int);
+    void setWidth(int, ExceptionState&);
+    void setHeight(int, ExceptionState&);
 
-    void setSize(const IntSize& newSize)
-    {
-        if (newSize == size())
-            return;
-        m_ignoreReset = true;
-        setWidth(newSize.width());
-        setHeight(newSize.height());
-        m_ignoreReset = false;
-        reset();
-    }
+    void setSize(const IntSize& newSize);
 
     // Called by Document::getCSSCanvasContext as well as above getContext().
     CanvasRenderingContext* getCanvasRenderingContext(const String&, const CanvasContextCreationAttributes&);
 
     bool isPaintable() const;
 
     enum EncodeReason {
         EncodeReasonToDataURL = 0,
         EncodeReasonToBlobCallback = 1,
         NumberOfEncodeReasons
@@ skipping 155 matching lines @@
     // Used for OffscreenCanvas that controls this HTML canvas element
     std::unique_ptr<CanvasSurfaceLayerBridge> m_surfaceLayerBridge;
 
     int m_numFramesSinceLastRenderingModeSwitch;
     bool m_pendingRenderingModeSwitch;
 };
 
 } // namespace blink
 
 #endif // HTMLCanvasElement_h